MOLECULAR-DYNAMICS IN K3C60 - A C-13 NMR-STUDY

Measurements of the C-13 NMR spectrum, spin-lattice, and spin-spin rel axation rates in K3C60 reveal the existence of two distinct molecular motions of the same C60 molecule above 200 K, with respective activati on energies of 2600 +/- 300 and 6800 +/- 500 K. We propose a simple mo del to explain these data implying fast axial jump rotation of the C60 molecules combined with slow jumps around perpendicular axes. The ana lysis of the spectra indicates an abrupt change in the molecular motio n below 200 K suggestive of a phase transition also evidenced by calor imetric measurements.